Microelectrode neural probes and interfaces are an essential tool in neuroscience. They typically comprise a multi-electrode array (MEA) configuration with exposed metal pads or electrodes located on rigid silicon shanks and connected, via interconnection traces, to output leads or to signal processing circuitry on a monolithic substrate. The exposed metal pads/electrodes provide a direct electrical interface with the neurons of a biological entity's nervous system to stimulate and/or record neural activity. Such neural probes can target the neuronal activity of neurons, enabling researchers and clinicians to better explore and understand neurological diseases, neural coding, neural modulations, and neural topologies, as well as treat debilitating conditions of the nervous system. Moreover, the ability to analyze neuronal activity using neural probes has led to the development of new neuro-therapeutic devices implemented through brain-machine interfaces. These interfaces use neural probes implanted to bypass damaged tissue and stimulate neural activity, so that a patient can regain lost communication and/or control with respect to some aspect of the patient's nervous system. Implantable neural probes and interfaces in particular enable extended interaction with neural tissue.
The flexibility of polymer-based intracortical neural implants provide an attractive alternative over conventional silicon-based neural probes and interfaces for reliable and stable long-term recording, stimulation, and/or monitoring of neuronal activities in the brain. Such flexible MEA probes are typically fabricated using multiple layers of polymers (e.g. biocompatible polymers such as polyimide, Parylene-C, and polyurethanes) coated layer by layer after each metal film deposition and patterning, to insulate the patterned conductive wiring and lines. The resulting electrode array is completely flexible and may enable extended interaction with neural tissue by mitigating the risk of silicon breakage and minimizing potential tissue damage caused by micromotion between the brain and the implant, for long-term safety and functional stability.
However, the low mechanical stiffness of flexible polymer-based MEAs can cause bending or buckling when percutaneously penetrated/inserted into tissue, e.g. the pial membrane of the brain. In particular, the viscoelastic and inhomogeneous properties of the brain make the mechanics of probe insertion a complex problem with direct insertion difficult.
What is needed therefor is an insertion tool and method for percutaneously inserting/implanting flexible devices by providing adequate stiffness to the flexible device to enable tissue penetration and insertion.